The present invention generally relates to a flexible circuit board, and more particularly to a flexible circuit board connecting another circuit board and a motor for which a body thereof must be rotated at time of adjusting a setting position thereof.
For example, in assembly processes of a magnetic disc unit, an alignment operation to determine an initial position of a head carriage supporting a magnetic head is performed. In this alignment operation, a magnetic disc for the alignment is loaded into the magnetic disc unit, the head carriage is properly moved for a distance less than a pitch of the tracks on the magnetic disc and the magnetic head is made to exactly face a reference track on the magnetic disc. Then, when the magnetic head has exactly faced the reference track, the alignment operation is over. In a case where the magnetic disc unit has a mechanism in which the head carriage is moved by a lead screw rotated by a stepping motor, the lead screw is properly rotated so that the alignment operation is performed. A constant voltage is applied to the stepping motor so that the motor shaft is magnetically locked. In this state, a body of the stepping motor is rotated around the center of the motor shaft at a small angle. Due to the rotation of the motor body, the lead screw is rotated.
The stepping motor is, for example, electrically connected to an external circuit by a flexible circuit board. A first connection portion at an end of the flexible board is fixed to terminals of the stepping motor by soldering or the like. A second connection portion at another end of the flexible board is connected to a connector on a printed circuit board on which a driving circuit of the stepping motor is formed. Then, a coupling portion of the flexible circuit board positioned between the first connection portion and the second connection portion is loosely wound around an outer surface of the stepping motor.
Since the stepping motor is rotated at a small angle at the time of the alignment operation, a distance between the first connection portion of the flexible circuit board and the second connection portion fixed to the printed circuit board changes. In other words, the degree of looseness of the coupling portion of the flexible circuit board changes according to the rotation position of the motor body. Thus, it is necessary to prevent the loose coupling portion of the flexible circuit board from interfering with other parts of the magnetic disc unit and from coming out of a housing of the magnetic disc unit. Japanese Laid-open Utility Model Application No. 1-165691 (The title of the invention is "A Guide Structure of a Flexible Circuit Board") discloses a structure having an engagement member with which the flexible circuit board is engaged on a base plate of the magnetic disc unit. Because of this structure's engagement member, it is possible to prevent the flexible circuit board from interfering with other parts of the magnetic disc unit and from coming out of the housing of the magnetic disc unit. However, in this proposed structure, it is necessary to particularly provide a guide member for guiding the flexible circuit board on the base plate of the magnetic disc unit so that the number of parts of the magnetic disc unit increases. Furthermore, the operation for making the loose portion of the flexible circuit board engage with the engagement member is required, so that the assembly operation of the magnetic disc unit is relatively troublesome.
In general, there are the same disadvantages, as has been described above, in a device having a flexible circuit board connecting another circuit board and a motor for which a body thereof must be rotated at the time of adjusting a setting position thereof.